A small drip from the relief valve drain line while the system heats is normal. A steady flow, water from the tank body or a pool around the base is not. If the tank itself is leaking, turn off the power or gas, close the cold water valve on the inlet and call a plumber: a leaking tank can’t be repaired.
Is it normal?
Water expands as it heats. On a storage hot water system, that extra volume has to go somewhere, so the relief valve or an expansion control valve lets a small amount out through a drain line while the system is heating. A few drips, or a small trickle during the heating cycle, is normal.
These are not normal:
- a constant flow from the drain line, even when the system isn’t heating
- water coming from the tank itself, its seams or its base
- a pool of water that keeps growing around the unit
- steam or very hot water spraying from any fitting
Where is the water coming from?
| Location | Likely cause | Urgency |
|---|---|---|
| Relief valve drain line, dripping while heating | Normal expansion | None, if it stops when heating stops |
| Relief valve drain line, flowing constantly | Worn relief valve, debris in the seat or high mains pressure | Soon: book a plumber |
| Expansion control valve on the cold inlet | Worn valve or high pressure | Soon |
| Pipe fittings and joints | Loose or corroded fitting | Soon, sooner if spraying |
| Tempering valve | Worn seals or internal failure | Soon |
| Tank body or base | The tank has corroded through | Urgent: the system needs replacing |
What to do right now
If the leak is more than a normal drip:
- Turn off the energy supply. For an electric system, switch off the hot water circuit at the switchboard. For gas, turn the gas control on the unit to off or pilot. Don’t touch switches with wet hands or while standing in water.
- Turn off the cold water supply. Close the isolation valve on the cold water pipe going into the tank. This stops the tank refilling.
- Keep clear of hot water. The water in the tank and pipes can be scalding. Don’t try to open the relief valve or drain the tank yourself.
- Protect the area. Move anything that could be damaged and put down towels or a tray if the unit is indoors.
- Call a licensed plumber.
Water where it shouldn’t be?
Turn off the water at the meter, then call Morrisons on 1300 149 288. We cover Caloundra to Maroochydore. Emergency plumbing.
Pressure relief valve problems
The relief valve is a safety device that opens if the temperature or pressure in the tank gets too high. It’s the most common source of a “leaking” hot water system. The usual causes are:
- A worn valve. Relief valves are commonly replaced about every five years as part of routine maintenance.
- Debris in the seat, which stops the valve closing fully. Gently easing the lever every six months helps keep it clear.
- High mains water pressure. If the water supply pressure is too high, the valve lets water out to protect the tank. A pressure limiting valve on the supply fixes the cause.
A plumber can test the incoming pressure and replace the valve on the same visit.
Repair or replace?
- Valves, fittings and pipework can usually be repaired or replaced, and the system keeps going.
- A leak from the tank body means the inner tank has corroded through. It can’t be patched, so the system needs replacing.
If you’re facing a replacement, our guide to hot water system cost explains pricing by type, and our guide on how long hot water systems last helps you decide whether it’s time.
Does insurance cover it?
Home insurance policies often cover sudden water damage caused by a failed hot water system, such as damaged flooring or cabinetry, but usually don’t cover the cost of the system itself, which is treated as wear and tear. Policies differ, so check yours and photograph the damage before cleaning up.
For a fast repair or replacement, see our hot water system repairs or call our emergency plumber line.
Frequently asked questions
Is it normal for a hot water system to leak?
A small amount of water from the relief valve drain line while the system is heating is normal, because water expands as it heats. A constant flow, water from the tank itself or a pool around the base is not normal and needs a plumber.
What should I do if my hot water tank is leaking?
Turn off the power at the switchboard for an electric unit, or the gas at the unit for a gas system. Then close the cold water valve on the inlet pipe to stop the tank refilling, and call a licensed plumber. Take care, because the water may be very hot.
Why is my pressure relief valve leaking?
A relief valve can leak because the valve is worn, debris is stuck in the seat, or the mains water pressure is too high. Relief valves are usually replaced about every five years. If high pressure is the cause, a pressure limiting valve may be needed.
Can a leaking hot water tank be repaired?
If the water is coming from the tank body, the tank has corroded through and the system needs replacing. Leaks from valves, fittings or pipework can usually be repaired.
Is a leaking hot water system an emergency?
A steady leak from the tank or a burst fitting should be treated as urgent, especially near electrics or inside the house. Turn off the power or gas and the cold water supply, then call a plumber.
Honest, upfront pricing from a local, family-owned plumber.
Call 1300 149 288 or request a quote. QBCC licence 1296541.